With a development and extensive use of various electronic products, secondary batteries are attracting a lot of attention as an energy source for such electronic products. Lithium-ion secondary batteries have been used as a representative secondary battery. Since this kind of secondary battery contains a variety of combustible substances therein, it may present various risks in terms of safety such as heat generation and explosion.
As an example, when overcharge occurs, which is one abnormal behavior of a battery cell, the overcharge gives a rise to gas generation in the battery cell owing to a chemical reaction of cell materials. This has an adverse influence on safety of the battery owing to the increased internal volume and temperature of the battery. In particular, because a pouch type of battery has an outer shell having a low physical strength and no safety feature of cell (circuit interrupt device (CID), positive thermal coefficient (PTC), fuse or the like), there is a need to provide a solution for solving overcharge problems.
In order to solve the problems, efforts have been made to the prevention of safety accidents caused by overcharge by improving structures of cell modules or packages. However, this kind of secondary battery still involves malfunction problems. Furthermore, although improvements can completely prevent safety accidents when the pouch type of battery expands abnormally, the electrical connection is established again with a gradual decrease in the volume of the pouch after the expansion, thus causing safety accidents due to flow of electricity.
Accordingly, there is a need to provide an improved technology capable of ensuring a high overcharge protection ability in the pouch type of secondary battery.
The foregoing is intended merely to aid in the understanding of the background of the present disclosure, and is not intended to mean that the present disclosure falls within the purview of the related art that is already known to those skilled in the art.